1. Field
The present invention relates generally to telecommunication devices, and in particular to telephones.
2. Background
Background noise is an inherent problem in wireless telephone communication. Conventional wireless telephones include a single microphone that receives a near-end user's voice and outputs a corresponding audio signal for subsequent encoding and transmission to the telephone of a far-end user. However, the audio signal output by this microphone typically includes both a voice component and a background noise component. As a result, the far-end user often has difficulty deciphering the desired voice component against the din of the embedded background noise component.
Conventional wireless telephones often include a noise suppressor to reduce the detrimental effects of background noise. A noise suppressor attempts to reduce the level of the background noise by processing the audio signal output by the microphone through various algorithms. These algorithms attempt to differentiate between a voice component of the audio signal and a background noise component of the audio signal, and then attenuate the level of the background noise component.
Conventional wireless telephones often also include a voice activity detector (VAD) that attempts to identify and transmit only those portions of the audio signal that include a voice component. One benefit of VAD is that bandwidth is conserved on the telecommunication network because only selected portions of the audio signal are transmitted.
In order to operate effectively, both the noise suppressor and the VAD must be able to differentiate between the voice component and the background noise component of the input audio signal. However, in practice, differentiating the voice component from the background noise component is difficult.
Furthermore, when a near-end user uses a telephone in a noisy environment, the far-end talker's voice can be difficult to understand due to the loud acoustic background noise of the noisy environment. A conventional technique uses the telephone microphone to pick up the background noise, then analyzes the noise to determine how to modify the far-end speech signal to improve its intelligibility.
A common problem in this high background noise condition, however, is that when the near-end user starts to talk, his voice will often be treated as noise, with the far-end user's voice being amplified or otherwise modified accordingly in an attempt to overcome this supposed “noise”. This can result in a shouting match between the near-end user and the far-end user. At the very least, the loudness of the far-end user's voice may be modulated by the near-end user's voice, resulting in unnatural loudness fluctuation. Although a VAD can be used for the near-end talker's voice, it is difficult to have reliable voice activity detection when the background noise is very loud.
Another problem is that the far-end talker may have a hard time understanding the near-end talker's voice since the near-end talker is in an environment with very loud background noise.
What is needed then, are telephones and methods that provide improved speech intelligibility. Such telephones and methods would desirably improve speech intelligibility, for example, when a user is located in a noisy environment.